Development of Column Packing Materials Using Functional Polymers and Application to Pharmaceutical Analysis

In high performance liquid chromatography (HPLC), packing materials based on porous silica gel are commonly used. Among them, ODS (OctaDecylSilyl)-modified silica gel, in which the silica-based material is chemically modified with octadecylsilyl groups, is the most widely used reverse-phase column due to its versatility in separating (bio)chemical compounds through hydrophobic interactions. The retention can be controlled by adjusting the ratio of organic solvents and aqueous solutions (typically with a pH range of 2–8) in the mobile phase. This principle is widely recognized and applied by chromatography researchers and practitioners. In contrast we have developed a novel concept of chromatography by surface-modifying the base of packing material with functional polymers. This review focuses on temperature- and pH-responsive chromatography using temperature- and pH-responsive polymers among stimuli-responsive polymers, as well as alkali-resistant column packing materials, which are developed by modifying the surface of porous calcium carbonate particles inspired by biominerals with amphiphilic polymers. First, the principles of elution control in 100% aqueous solutions through external stimuli (temperature and pH) in temperature- and pH-responsive chromatography, as well as its application to the separation of small molecules and proteins are discussed. Subsequently, it introduces the development of novel packing materials by electrostatically adsorbing poly(maleic acid-alt-1-octadecene) (PMAcO) onto the surface of synthetic porous calcium carbonate microspheres and eggshell powder, and their application to the separation and preparative purification of basic compounds using alkali mobile phases.